The present invention relates to a hip joint prosthesis comprising a femoral component having a shank formed of a metal alloy and a joint head, said joint head adapted to cooperate with either the natural acetabulum or a prosthetic acetabulum likewise formed of a metal alloy.
The basic construction of the femoral portion of a hip joint endoprosthesis is typically the same. The shank is anchored with or without bone cement in the proximal femoral canal. A radially projecting collar serves as an abutment for limitng the extent of insertion during impaction. The joint head is typically formed by a joint ball formed integrally with the shank or by a separate joint ball fastened at the neck of the femoral component. The joint head for its part cooperates with the natural acetabulum or a prosthetic acetabulum. It is known to design the prosthetic acetabulum to be bipartite, with a preferably metallic outer portion anchored in the hip bone, while a flexible inner portion accommodated by the outer portion accommodates the joint head in snapping engagement.
It is known to anchor the prosthesis shanks in the femur canal with the aid of bone cement. As the danger exists that after a longer period of time a loosening may occur between the prosthesis shank and the bone cement due to constant dynamic load, it has already been proposed to fasten the prostheses without bone cement by positively accommodating the femur shank in the femur canal. This may be carried out, for instance, with the aid of a relatively long shank.